Made for hearty souls who laugh at sub-zero wind chills. Sleet, freezing rain, snow? Keep it comin'. Our Mountaineering sock simply doesn't back down. Extra heavy terry loop construction protects the entire foot for maximum warmth. While the other guy's "extreme cold weather" socks feel more like Moon Boots ours have a streamlined performance fit that keeps up with you in the worst of weather. No slipping, no bunching, no blisters. Fine gauge Merino Wool makes this a fast drying, breathable sock that stays warm in the winter and amazingly cool in the summer. And since Merino Wool is naturally antimicrobial this sock repels bacteria and odor - a great feature when you need to get any extra day (or two) out of your socks. Still made in Vermont. Guaranteed for life.